On the Role of Relative Prices and Capital Flows in Balance-of-Payments Constrained Growth: the Experiences of Portugal and Spain in the Euro Area

Broadly speaking, the balance-of-payments constraint hypothesis as developed by Thirlwall has been empirically supported. Yet, it shows some shortcomings highlighted in the literature. In our opinion, two of them must be analysed. First, temporary disequilibria and capital flows must be incorporated into the balance-of-payments constrained growth models. Second, the role of relative prices must be made explicit, since it can be relevant even in an external constraint framework. This study is aimed at developing a model that incorporates both possibilities: temporary external disequilibria and a the impact of relative prices. This model is subsequently used to analyse the evolution of the Spanish and Portuguese economies in last decades, and, in particular, the different path shown by both countries since their accession to the Eurozone.Pese al respaldo empírico con el que ha contado la teoría de la restricción externa desarrollada a partir del modelo de Thirlwall, éste muestra algunas deficiencias destacadas en la literatura. En nuestra opinión, dos de ellas merecen ser analizadas. Por un lado, la necesidad de incorporar desequilibrios transitorios de la balanza de pagos y los consiguientes flujos de capital. Por otro, creemos los precios relativos pueden desempeñar un papel importante en el comercio exterior, sin que ello invalide la existencia de una restricción externa. El objetivo del presente trabajo consiste en desarrollar un modelo que incorpore ambas cuestiones, permitiendo, así, un mayor protagonismo a los precios relativos y a los desequilibrios temporales de la balanza de pagos. Este modelo se emplea posteriormente para analizar la evolución de las economías española y portuguesa en las últimas décadas y, en especial, las diferencias mostradas desde su incorporación a la Eurozona.Growth, Balance of payments constraint, Exchange rate.

Polariton excitation in epsilon-near-zero slabs: transient trapping of slow light

We numerically investigate the propagation of a spatially localized and quasi-monochromatic electromagnetic pulse through a slab with Lorentz dielectric response in the epsilon-near-zero regime, where the real part of the permittivity vanishes at the pulse carrier frequency. We show that the pulse is able to excite a set of virtual polariton modes supported by the slab, the excitation undergoing a generally slow damping due to absorption and radiation leakage. Our numerical and analytical approaches indicate that in its transient dynamics the electromagnetic field displays the very same enhancement of the field component perpendicular to the slab, as in the monochromatic regime. The transient trapping is inherently accompanied by a significantly reduced group velocity ensuing from the small dielectric permittivity, thus providing a novel platform for achieving control and manipulation of slow light

Estudar e Trabalhar na It\ue1lia: instrumentos e procedimentos para a inclus\ue3o de pessoas com defici\ueancia Studying and living in Italy: tools and procedures to include disabled people

Italy is known for the best practices on educational and la- bour inclusion. An organic set of laws allows a full access to education and work, ensuring rights and necessary re- sources to disabled people, their families and organisations hosting them. The evolution of the Italian regulatory frame- work has resulted in the development of a theoreticand conceptual structure on special pedagogy and didactics, to follow the constant changes and demands of the institu- tions and society. This paper examines the evolution of laws that transformed Italy in the forefront in social inclusion as well as the different moments and scope of them concern- ing the participation of people with disabilities in education and work

A quark model analysis of the Sivers function

We develop a formalism to evaluate the Sivers function. The approach is well suited for calculations which use constituent quark models to describe the structure of the nucleon. A non-relativistic reduction of the scheme is performed and applied to the Isgur-Karl model of hadron structure. The results obtained are consistent with a sizable Sivers effect and the signs for the u and d flavor contributions turn out to be opposite. This pattern is in agreement with the one found analyzing, in the same model, the impact parameter dependent generalized parton distributions. The Burkardt Sum Rule turns out to be fulfilled to a large extent. We estimate the QCD evolution of our results from the momentum scale of the model to the experimental one and obtain reasonable agreement with the available data.Comment: 31 pages, 4 figures. Extended version, discussion of the Burkardt Sum Rule added, references added, minor changes in the numerical results, same interpretation. Final version accepted for publication in Phys. Rev.

Why Should a Firm Choose to Limit the Size of its Market Area?

We study when a monopolistically-competitive firm may optimally choose to limit the size of its market. This may be the case when the cost of serving the market with geographically dispersed customers is increasing in size. We also investigate the incentives faced by a firm to limit the reach of its market, when it adopts different pricing schemes. We show that under certain assumptions the derived equilibria are constrained socially optimal.Monopolistic competition; Transport costs; Endogenous fixed costs; Overlapping market areas

One-Dimensional Super Calabi-Yau Manifolds and their Mirrors

We apply a definition of generalised super Calabi-Yau variety (SCY) to supermanifolds of complex dimension one. One of our results is that there are two SCY's having reduced manifold equal to $\mathbb{P}^1$, namely the projective super space $\mathbb{P}^{1|2}$ and the weighted projective super space $\mathbb{WP}^{1|1}_{(2)}$. Then we compute the corresponding sheaf cohomology of superforms, showing that the cohomology with picture number one is infinite dimensional, while the de Rham cohomology, which is what matters from a physical point of view, remains finite dimensional. Moreover, we provide the complete real and holomorphic de Rham cohomology for generic projective super spaces $\mathbb P^{n|m}$. We also determine the automorphism groups: these always match the dimension of the projective super group with the only exception of $\mathbb{P}^{1|2}$, whose automorphism group turns out to be larger than the projective general linear supergroup. By considering the cohomology of the super tangent sheaf, we compute the deformations of $\mathbb{P}^{1|m}$, discovering that the presence of a fermionic structure allows for deformations even if the reduced manifold is rigid. Finally, we show that $\mathbb{P}^{1|2}$ is self-mirror, whereas $\mathbb{WP} ^{1|1}_{(2)}$ has a zero dimensional mirror. Also, the mirror map for $\mathbb{P}^{1|2}$ naturally endows it with a structure of $N=2$ super Riemann surface.Comment: 50 pages. Accepted for publication in JHE

Robustness of large-scale stochastic matrices to localized perturbations

Upper bounds are derived on the total variation distance between the invariant distributions of two stochastic matrices differing on a subset W of rows. Such bounds depend on three parameters: the mixing time and the minimal expected hitting time on W for the Markov chain associated to one of the matrices; and the escape time from W for the Markov chain associated to the other matrix. These results, obtained through coupling techniques, prove particularly useful in scenarios where W is a small subset of the state space, even if the difference between the two matrices is not small in any norm. Several applications to large-scale network problems are discussed, including robustness of Google's PageRank algorithm, distributed averaging and consensus algorithms, and interacting particle systems.Comment: 12 pages, 4 figure